7 A BRIEF HISTORY AND CURRENT PRACTICE OF SATURATION T DIVING AND UNDERSEA LIVING Dick Clarke Columbia, South Carolina, USA he development and introduction of a technique termed saturation diving revolutionized many aspects of diving operations. It allowed underwater work to be conducted in much deeper depths than were otherwise attainable by conventional surface orientated diving operations. It allowed complicated and lengthy projects to be completed much more quickly, far more effectively and with improved safely and it greatly expanded the research capabilities of marine scientists, allowing them to actually live and work within the environment they wished to study, in depths far down on the continental shelf. Concept The concept of saturation diving is really quite simple. A good analogy is that of a sponge which is immersed in water. The sponge will continue to absorb water until it becomes completely saturated (full). Once this point is reached continued immersion, no matter if it is for hours, days, or weeks, will not increase any further the amount of water that can be squeezed out of the sponge upon its removal from the water. Now substitute the diver for that sponge. As a diver spends time underwater, his body tissues will gradually and continually absorb the inert gas present within his breathing supply. For an air dive, this gas will be nitrogen. For a very deep dive it will likely be helium. The longer the diver remains underwater the greater the amount of inert gas is absorbed, so too the amount of time required for the diver to safely decompress back to the surface. If the diver remains underwater long enough his tissues will eventually become fully saturated with inert gas, as did the sponge. When this point is reached, the decompression obligation time becomes fixed. No matter how much longer the diver remains at depth, be it hours, days, weeks, there will be no additional decompression time required to return to the surface. Types of Saturation Diving There are two fundamental methods in which saturation diving is employed and divers are able to live and work under elevated pressures/depths. One is most commonly employed in commercial, professional and military diving operations. The second has long been used by marine scientists and earlier pioneering naval diving operations. SBT

8 The first method is to compress divers to the desired saturation (work site) depth in a surface located hyperbaric chamber, commonly positioned on a support vessel, production platform or oil rig. Here they will live, eat and sleep when not working in the water. The period of time that they will remain in saturation depends upon the amount of work required, in most cases it will be several weeks. If the work requirement is expected to take less than approximately 30 days, the initial team of divers will remain in saturation and complete the full scope of the work. If the project requires many more weeks or months to complete, then separate teams of divers will be rotated in and out of saturation, commonly on a 30 day cycle. To actually get to the worksite from the chamber, divers enter a diving bell that has been attached to the chamber and pressurized to the same depth as the living chamber/work site depth. Once inside the diving bell, hatches are secured and the bell is lifted away from the main chamber. The bell is then quickly lowered to the worksite. Quickly, because it is under a high pressure compared to its surroundings so if there is any damage to the bell or it otherwise develops a leak during transfer, resulting uncontrolled decompression could be catastrophic to the divers inside the bell. Upon its arrival at the planned work site, the pressure inside the bell will now equal water depth to which it has been lowered. At this point the hatches can be opened and the diver(s) enters the water and proceed with his task. Commonly, the bell will remain at the worksite for eight hours. At this point the diver(s) returns to the bell and its hatches are secured. The bell is then quickly hoisted to the surface (while maintaining the worksite saturation pressure inside). It is then reattached to the surface living chamber. The divers re enter the chamber, shower, and report their work product to supervisors and engineers who are stationed in the chamber control room. They will then eat a meal that has been transferred into the chamber via a small access lock, watch a movie (projected through a chamber view port) then go to sleep. In most cases, another team of divers have already transferred from the chamber to the bell and are now at the worksite. With three teams of divers (usually working as two man teams) in saturation, this process is undertaken 24 hours a day, with at least 22 hours being actually productive at the worksite (the remaining two hours representing the time taken for bell transfers). If the initial team of divers can complete all of the underwater work, they will then be decompressed back to surface pressure, commonly in the main living chamber. For several weeks of underwater work, there will be only one decompression (a very slow one, taking about 24 hours for each 30 metres in saturation depth). As decompressions from deep dives are somewhat hazardous, having to undergo only one represents a distinct safety advantage, in contrast to decompressing daily when surface orientated bounce diving is employed. And SBT

9 saturation decompression procedures carry a much lower risk and severity of decompression sickness that surface oriented deep dive decompressions. If the underwater work will take several months to complete, then the first team of divers will be decompressed in an adjacent chamber after approximately 30 days, and a second team of divers pressured up to saturation depth, to replace them. The second saturation diving method is to actually live at the work site. This is accomplished by the use of an underwater habitat (house). The habitat is placed on the seabed and divers are transferred to it either by swimming down (if the depth is less than approximately 45 metres), or by a diving bell or small submersible (submarine). All of the environmental and operational needs of the habitat are provided by a surface located support system that is connected to the habitat by an umbilical connection of several hoses and cables. Aquanauts exit the habitat daily and may spend as many as hours in the water each day. Scientific studies are conducted daily from the habitat, with the divers (aquanauts) returning to it to eat and rest. Diving commonly takes place in the direct vicinity of the habitat. It can also be conducted some distance away and in both shallower (upward excursion) and deeper (downward excursion) depths than the habitat saturation level. Special decompression tables are required to safely carry out these excursions and they may require an underwater vehicle (lock out mini submarine or wet submarine) to make the excursions effective. Upon completion of their saturation dive, the aquanauts will be returned to the surface in one of two ways. If the saturation/work site depth is less than metres, the habitat s hatches are sealed and the internal atmosphere is gradually reduced via a hose within the umbilical cord, up to the surface. Saturation decompression times are identical to those in the previously described saturation diving method (approximately 24 hours for every 30 metres in depth). Once the internal habitat atmosphere has equaled equivalent surface pressure, the aquanauts enter an transfer lock in the habitat and are quickly compressed back to original saturation/seabed pressure. They then exit the habitat and swim up to the surface. When the habitat saturation depth is deeper than 30 metres, it is not possible to exit the habitat as described above because of the very likely risk of incapacitating/fatal decompression sickness. So, a diving bell or small submersible returns to the seabed. The divers swim over and enter the vehicle, its hatches are sealed and the vehicle is quickly returned to the surface, all the while maintaining original saturation pressure inside. The vehicle is then mated (connected) to a hyperbaric chamber that has been previously pressurized. Once inside the chamber, the divers are decompressed in relative comfort. In one particular design the vehicle could connect (mate) directly onto the habitat so that a dry transfer could be affected. SBT

10 Historical Perspective Dr. J. Scott Haldane created the very first decompression tables, on behalf of the British Royal Navy, in During his research Haldane recognized that eventual tissue saturation would occur if a diver spent sufficient time at increased pressure (depth). This observation represented the first time the concept of saturation diving was considered. This concept was not pursued any further at this time as there was no interest or need in diving to great depths or for long periods. It was in 1938 that the first saturation dive was made. Construction of underground subways, tunnels and supports for bridges to span rivers could only be undertaken in a compressed air environment. This was to prevent the surrounding water from entering and flooding the tunnel or caisson as it was constructed. Men working in these compressed air environments were at risk of decompression sickness in the same manner as divers are today. In fact, when this type of tunnel and caisson work first began, in the mid 1800s, thousands of workers suffered decompression sickness and hundreds died. Things improved greatly when formal decompression procedures were introduced. It was common practice to use donkey and mules to haul away rock and earth as excavation progressed. These animals remained under pressure for weeks and months at a time while the men were decompressed daily. When the animals were eventually returned to the surface they immediately died. To determine if a slower rate of decompression would allow these animals to survive, two individuals spent 27 hours at 30 metres in a research chamber, effectively saturating their tissues at this pressure. Following what was considered a lengthy (at the time) five hour ascent decompression sickness occurred. Clearly, there was much still to be learnt about saturation diving and subsequent decompression procedures. This work did indeed serve to improve survival of the animals. The first systematic evaluation of the concept of saturation diving (and remains the most comprehensive even today) was undertaken by the U.S. Navy, beginning in It was called Project Genesis and headed by Dr. George Bond, fondly remembered as the father of saturation diving. Project Genesis The initial steps in this research were designed to confirm that breathing compressed air would be unsuitable at the depths that saturation diving was be expected to be undertaken. Oxygen represents 21% of the atmosphere (producing an oxygen pressure of 159 mmhg). As the pressure at which air is breathed increases, the percentage of oxygen remains constant, but its partial pressure increases as depth increases. For every additional 10 metres of depth there is a corresponding 159 mmhg in oxygen pressure inspired by the diver. If oxygen pressures become high enough, or duration of time spent at intermediate pressures is long enough, oxygen becomes poisonous (to the lungs and to the brain). SBT

11 Step one of Project Genesis (A1) was to take rats to 60 metres, breathing compressed air. Within 35 hours they had all died as a result of oxygen damage to their lungs. To confirm that the high oxygen pressure in compressed air was indeed the problem, another group of rats (A2) were taken to the same pressure (60 metres) but breathed only 3% oxygen, the 97% balance being nitrogen. In terms of inspired oxygen pressure, 3% at 60 metres is equivalent to breathing 21% oxygen at normal sea level. All of the rats survived. It did appear that the concentration of oxygen (21%) at this degree of increased pressure was the problem. One final step in the confirmation process (A3) was to have rats breathe 100% oxygen at 5 metres (the equivalent oxygen pressure that would be present in compressed air at 60 metres). All the rats died after 35 hours. This clearly demonstrated that compressed air could not be used. The percentage of oxygen in any breathing gas supply, therefore, must be diluted (maintained as close to normal sea level pressure; 159 mmhg) because of its otherwise poisonous and potentially lethal effects. The other problem with compressed air was related to increasing nitrogen pressures, as depth increased. Every diver understands that nitrogen will eventually become narcotic if compressed air is breathed at deep enough depths. When the percentage of oxygen is reduced, to avoid its toxic effects, the percentage of nitrogen in the breathing gas is correspondingly increased. So, breathing 3% oxygen at 60 metres is equivalent to breathing compressed air at a much greater (and more narcotic) depth. Not a good thing! So the next part of Project Genesis was to replace nitrogen. Helium was the logical choice as it had already been used by the U.S. Navy, beginning the late 1930 s, for brief surfaceorientated dives. The plan to have divers live and work in a helium oxygen atmosphere for extended periods was somewhat controversial, however. Very prominent scientists of this era were of the firm belief that humans could not live in an atmosphere that did not contain substantial amounts of nitrogen. Study (B1) tested this concept, again using rats. These animals were maintained in a hyperbaric chamber at normal sea level pressure while breathing 20% oxygen and 80% helium for a period of 16 days. All the rats survived. The next group of rats (B2) was exposed to 3% oxygen and 97% helium at 60 metres for 14 days. All of these rats survived. The final animal study during Project Genesis (B3), involved some larger animal species (a goat, a monkey and more rats) and also exposed to 3% oxygen/97% helium at 60 metres for 14 days. All of these animals survived. As they had survived without nitrogen all was now in place for the first study of humans saturated within a helium oxygen environment. Formal approval from the U.S. Navy was granted to Dr. Bond and his colleagues in Project Genesis Phase C first involved saturating three divers at normal atmospheric pressure (as per B1, above) inside a laboratory based hyperbaric chamber for a period of six days. They breathed 21% oxygen, 74% helium and 4% nitrogen. The nitrogen was there not by design, they were using too much costly helium to try and wash out all of the nitrogen SBT

12 from the atmosphere. All went well, although the divers constantly complained of being cold (helium conducts heat more readily than nitrogen) and voice communications were difficult, because of the effect of helium on the vocal cords (causing the vocal cords to resonate at a greater level than with air, and the voice pitch increasing accordingly often creating sounds like the Disney character Donald Duck). With the successful completion of Phase C, Phase D began. Here, three divers were saturated in the same laboratory chamber at 30 metres for six days. They lived in and breathed an atmosphere containing 7% oxygen, 7% nitrogen and 84% helium. An adjacent water filled chamber pressurized to the same depth allowed the divers to conduct in water exercises, in order to determine if work performance could be maintained in this type of environment. All went well, except the same complaints of being cold and struggling with voice communications (which prompted successful research to develop helium voice unscrambler ). The last aspect of Project Genesis, Phase E, was the final laboratory chamber saturation dive. This time, three divers were maintained at 60 metres for 12 days, breathing 3.9% oxygen, 6.5% nitrogen and 89.6% helium. All went well except the fact that they were again very cold and at this saturation depth communication with the outside chamber support personnel was virtually impossible. All were safely decompressed, taking 27 hours. Open Ocean Saturation Diving No one was paying more attention to the U.S. Navy s saturation diving research more closely than Edwin Link and Jacques Ives Cousteau. Ed Link was the American aviation pioneer who had created the first aircraft flight simulator (the Link Trainer), in He had subsequently turned his attention to the oceans but was constantly frustrated with the very short bottom (diving) times available for his divers. So he proposed to put man in the sea, safely, deep and long enough to do useful work. And he proceeded to do just this once he was aware of the successful completion of the laboratory phases of Project Genesis. In 1962, one of his dive team members spent 24 of a planned 48 hours in a chamber suspended 60 metres below Link s support vessel Sea Diver, off the French Mediterranean coast. The diver breathed 10% oxygen, 87% helium and 3% nitrogen. He made several downward excursion dives to a maximum of 75 metres. The saturation dive was largely successful although aborted early due to an approaching storm. Jacques Ives Cousteau is well known to divers and non divers alike. Among his many accomplishments he is credited with pioneering the use of SCUBA diving. Just four days after Link s first open water saturation dive and 160 kilometers further along the French Coast, Cousteau embarked on a series of experiments called Pre Continent. The first one was named Conshelf I. This habitat was lowered to 10 metres from a surface support vessel, where two divers spent seven days, breathing compressed air. This depth was shallow enough that the oxygen pressure in compressed air was not poisonous. An average of five hours each day was spent in the water and excursion dives down to 55 metres were SBT

13 undertaken. There were no hatches in Conshelf I, so to decompress the divers the habitat was slowly hoisted back to the surface, with a habitat and man decompression stop at 3 metres. Nine months after Conshelf I came Conshelf II. This was the first habitat actually located on the seabed, the others had been suspended from a surface vessel. Conshelf II was placed on the seafloor off the coast of Sudan, in the Red Sea, at a depth of 10 metres. Six aquanauts spent 30 days in Conshelf II breathing air. Two of the aquanauts spent seven of the 30 days in what was called Deep Cabin, a small chamber located at 110 metres breathing a helium oxygen mixture. The last of Cousteau s Pre continent I studies was Conshelf III, which began in It was placed in 102 metres off the coast of Monaco, in the Mediterranean. As Cousteau s first two habitat dives had demonstrated that man could survive without difficulties in a saturation environment, Conshelf III s primary objective was to attempt to perform useful work. A key project was an oilfield wellhead assembly, which was placed in close proximity to the habitat. Six aquanauts spent three weeks successfully performing all of their required tasks. Unique to Conshelf III were two small (three person each) chambers that could be detached and surfaced in an emergency, the forerunner to hyperbaric lifeboats that have now becme commonplace in oilfield diving operations, particularly in the North Sea. Ed Link had also been busy during this period. In 1964 his second saturation dive took place in the Bahamas. Two aquanauts lived inside a Submersible, Portable, and Inflatable Dwelling (SPID), suspended from Link s support vessel at a depth of 130 metres. They remained there for 49 hours in very cramped and uncomfortable quarters. They were then recovered with the aid of a diving bell and transferred under pressure to a hyperbaric chamber on vessel floating above. Decompression took 92 hours. It should have not been too surprising that Link and Cousteau had been able to conduct open water saturation dives before the U.S. Navy. The navy was and remains a large bureaucracy and the decision making process to approve open water saturation diving was slow. There was no such bureaucracy for Link and Cousteau to deal with. Once they had been made aware of the U.S. Navy s successful laboratory research they immediately laid plans for their habitat experiments. With the tragic loss of the U.S.S. Thresher, a nuclearpowered submarine, in April 1963, however, the U.S. Navy suddenly became much more interested in deep submergence search, rescue and recovery capabilities. Approval to proceed with the open water phase of Dr. Bond s pioneering research was received this same year. The U.S. Navy s first underwater habitat was named Sealab I. It was a very basic design (two pontoon floats welded together). There were two entrances but no hatches that could SBT

14 secure the internal atmosphere. Aquanauts, therefore, had to be recovered from the habtat by a diving bell in order to safely undergo decompression (within a hyperbaric chamber on a surface support vessel). Sealab I was placed on the seabed in 58 metres, off the coast of Bermuda, in the North Atlantic. Four aquanauts lived in a helium oxygen atmosphere for 11 days. An approaching storm caused the dive to be aborted somewhat earlier than planned, but the project was otherwise successful. Next up for the U.S.Navy was Sealab II, a purpose built underwater habitat that was much more sophisticated and capable than its predecessor. In 1965 it was placed in 60 metres off the Californian coast. Three ten man teams lived in Sealab II for 15 days each. This was the most complex series of saturation dives to date. The navy was now confident that seabed living offered important operational, engineering and scientific advantages. So additional human physiology studies, and technical, salvage, and marine science operations were undertaken. It was also the first saturation dive that combined sailors and scientists, which made for an interesting dynamic at times! Sealab II s aquanauts were transferred under pressure to and from the habitat by a diving bell from an overhead vessel s hyperbaric chamber complex. One very unique aspect of Sealab II was the support of Tuffy, a bottlenose dolphin. Tuffy had been trained to transfer supplies to and from the habitat, between aquanauts while they were in the water, and to come to the aid of an aquanaut that might be in distress. Tuffy s performance was not always consistent, but always well intentioned! Sealab II was considered a great success so the habitat was completely refurbished and extensively upgraded to become Sealab III. The planned depth for Sealab III was three times deeper than Sealab II, namely 185 metres. Because of the additional challenges of this depth, a series of biomedical and performance validation dives were conducted at the U.S. Navy s Experimental Diving Unit, in Washington D.C. Sealab III was lowered to 185 metres off San Clemente Island, California, on February 15, Before being occupied, it had become apparent that the habitat was leaking significant amounts of gas. A mini submarine was sent down to make an inspection. The submarine noted helium leaks around several electrical penetrators. Four of the eight aquanauts who were about to be pressured up within the surface chamber system in anticipation of transfer to Sealab III were selected to make necessary repairs. They underwent an accelerated compression schedule in the surface saturation storage chamber then transferred via a diving bell. Two exited the bell at 185 metres breathing a helium oxygen mixture via a closed circuit re breathing system. The initial plan was for the aquanauts to wear electrically heated suits but they were eventually considered to be unsafe. So, as incredible as it seems today, they wore wetsuits (at 185 metres!) because the bell had not been set to support hot water suits. At this great depth, the suits would have been SBT

15 compressed to an almost paper thin size, thereby incapable of providing any reasonable degree of thermal protection. Loss of insulation in this manner, the very cold water and the use of helium (a potent thermal conductor) all served to compound diver cooling to a dangerous degree. Unfortunately, the divers could not open the habitat hatch in order to gain entry and begin the repair processs. This was likely the result of an imbalance of pressure between the habitats s internal atmosphere and the surrounding water pressure. By now, the divers were extremely cold, so they were forced to return to the diving bell and were transferred under pressure back to the surface saturation storage chambers, both divers being in a significant state of hypothermia. The habitat had already lost over half a million cu. ft. (14,200 cubic meters) of helium at this point, so there was great urgency to get the leaks repaired as surface supplies were running low. The same four divers were returned to the seabed just six hours later, and the same two left the diving bell. Within moments of exiting the bell one diver collapsed, suffered seizures and lost all purposeful movements. He was recovered to the bell where cardiopulmonary resuscitation was started (in an upright position in a very tight space!). He did not survive. A subsequent investigation revealed that the carbon dioxide absorbent canister in his closed circuit rebreathing system had not been refilled after the first dive a glaring operational error. This tragic event and other political issues resulted in the U.S. Navy discontinuing further interest in seabed habitats. The Navy did not abandon saturation diving technology altogether, however, as will become apparent a little later in this presentation. Commercial Civilian Saturation Diving The first true working saturation dive took place in fresh water, It was undertaken at the newly constructed Smith Mountain Dam, in Virginia, USA. Design of the dam s trash racks, devices that prevent debris from entering the hydraulic turbines that generate power, was faulty and they had to be removed and replaced. A unique saturation diving system was designed and built by Westinghouse Corporation for this project. It proved to be so very successful that it became the standard design for all of the early saturation diving systems used in the commercial offshore diving industry. This particular saturation dive was also the first to incorporate hot water heated diving suits. Two four man teams rotated one week in and one week out of saturation, for a period of four months. The storage chamber, diving bell, and breathing gas supply was helium and oxygen. Water depths ranged from metres and bottom times extended up to five hours for each diver. It had been estimated that it would have taken two years to drain the dam in order to make the necessary repairs. It was also estimated that surface orientated operations would have required 32 divers and nine months to complete the work. This project was acknowledged to be so operationally and economically successful that it immediately caught the attention of the offshore oil and gas industry. Within one year this same diving system was used for the world s first offshore SBT

16 oilfield saturation dive, in the Gulf of Mexico. Soon thereafter, the global commercial oilfield diving industry was routinely employing this technology, and on an international scale. By far the most common user of saturation diving today is the offshore commercial diving industry, through its support of oil and gas drilling and production operations. Diving systems have evolved to the point that a single complex can accommodate 16 or more divers and can operate two diving bells (so able to simultaneously support work at two separate underwater locations and depths). It can decompress one dive team while a second team remains operational (further increasing efficiency). A system such as this can launch and recover the bell(s) in high winds and heavy sea states (eliminating much lost work time due to bad weather). And it can incorporate a detachable, evacuation lifeboat, should a catastrophe occur (oil rig fire/explosion; wellhead blowout; collision) that may place vessel, oil rig or production platform supporting the diving system in danger of collapse or sinking. Oilfield saturation diving has become increasingly common for work that is expected to take many weeks to several months to complete, even in relatively shallow (less than 60 metres) waters. In some cases, such as platform inspections in a region where many platforms coexist, underwater work requirements never end. Once all the platforms have been inspected it is time to start the inspection cycle again. Saturation diving is really the only practical method in which to support this endless work load. Saturation diving has also replaced much of the deep (greater than metres) surface orientated bounce diving. This is the technique where divers enter the bell and are lowered to the work site while the bell is maintained at normal sea level pressure. Once in position the bell is quickly pressurized, the diver exits the bell to work, then quickly returns to the bell (quickly, due to the very limited bottom time available because of limitations in available decompression tables). As soon as the bell begins its journey to the surface and its internal pressure becomes higher than the surrounding water, the divers will start their own decompression, venting gas into the surrounding water. Upon its arrival at the surface, the bell is attached to a surface chamber. The divers make the transfer and complete the remainder of their decompression obligation in relatively comfortable surroundings. For these deeper dives very little bottom time is available and very lengthy decompressions are required. By way of example, a 150 metre dive has a maximum available bottom time of only 30 minutes, and a corresponding decompression obligation of 14 hours. There is no addition bottom time beyond the 30 minutes. If the divers do not begin their decompression within that 30 minute time frame the only remaining option to bring the divers safely back to the surface is a saturation diving table this would mean a decompression of 120 hours instead of 14! The oil company that is employing the diving contractor is going to be very unhappy at the associated increase costs! Seabed Scientific Diving The first significant marine science underwater habitat program was called Tektite The habitat was designed and built by General Electric Corporation, in the U.S. In 1969 Tektite I SBT

17 was placed in a depth of 15 metres off the coast of the U.S. Virgin Islands, in the Caribbean Sea. Air was the habitat atmosphere. Four civilian aquanauts spent a record 58 days conducting biomedical and marine science studies. Tektite II was a follow up project in 1970, using the same habitat. It was funded, in large part, by the U.S. government agency National Aeronautics and Space Administration. NASA was interested in the long term effects of isolation as it prepared for deep space missions. The underwater habitat was thought to be a useful simulation of this type of isolation. Tektite II was an ambitious effort. It involved ten separate missions, each lasting days. One of the missions involved the first all female aquanaut team. A great deal of science was conducted and many publications have reflected the resulting scientific findings. The next prominent program involved the Hydrolab habitat. It went on to become the most enduring and most widely used of all undersea living programs, lasting for 15 years and home to over 500 scientists. Hydrolab was also the most economical. An autonomous (unmanned) surface support system provided all of the habitat s necessary services and utilities. The entire program was supported by just two shore based personnel. Hydrolab was built by Perry Oceanographics in Florida. It was placed in 14 metres off the southern shore of Grand Bahama Island, in 1971, and compressed air was again the internal atmosphere. Hydrolab was located within a series of magnificent coral reefs, a little less than one kilometer from the very edge of the continental shelf. Teams of three or four aquanauts spent between seven and 10 days in saturation. A unique feature of the habitat was a connector that allowed a mini submarine to mate directly on to the habitat. This feature was designed to allow an emergency evacuation of one or more of the aquanauts, as well as the transfer of scientists to and from the habitat who had not learnt how to dive. After a year or so of studying the surrounding ecosystem and various physiologic responses, aquanauts began to range further and further from the habitat. Initially this was simply by SCUBA. Eventually it involved transfers by various wet and dry mini submarines. Some of these excursions went down the continental shelf, where the deepest (75 metres) compressed air lockouts were undertaken. Bottom time was plentiful on these deep dives as the decompression was only back to 14 metres, not all the way up to the surface. Hydrolab was the scene of the first and only descending excursion dives from saturation that required decompression stops to return to the habitat storage depth. Other notable undersea living programs included the German Helgoland (used in the Baltic Sea and off the U.S Northeast Coast). The second death of an aquanaut occurred during Helgoland s deployment in the U.S.A. In this instance, the aquanaut had completed inhabitat decompression at the end of his mission. He had been recompressed back to seabed depth, had locked out of Helogland and was ascending to the surface holding on to a line that ran from the surface to the habitat. The sea state involved 4 metre high long period waves from an approaching hurricane. As he neared the surface he apparently inhaled at the SBT

18 time the peak of the wave was directly above him, while holding on to the fixed line. He remained at about the same point on the line as the subsequent wave tough passed over him, but he did not exhale. This produced a large intra pulmonary pressure, resulting in pulmonary barotraumas induced cerebral arterial gas embolism (similar to that which a diver might experience if he rushed to the surface without adequate exhalation). He did not survive resuscitation attempts. La Chalupa was operated off the coast of Puerto Rico for several years during the 1980 s. Sub Igloo and Lora 1 were two Canadian built and operated habitats that saw brief periods of activity under the Arctic icecap. On one occasion Sub Igloo was located at the North Pole. It was then briefly transferred to the Bahamas and placed on the edge of the continental shelf, serving as an underwater way station for an ambitious project with Hydrolab as its centerpiece. Aquarius was the world s last habitat program. It was built in Texas in 1986 and originally named the George F. Bond, in recognition of the father of saturation diving. Underwater operations were planned off the coast of Catalina Island, Southern California, but switched to the Virgin Islands, in the Caribbean Sea, where it spent two years. Its saturation depth was 20 metres. In 1989 a hurricane devastated the region and the habitat was returned to the U.S., for repairs and refurbishment. If remained out of use for several years before being placed in the Florida Keys, again at 20 metres. It was used for a variety of marine science, engineering and biomedical projects. It was also used by NASA astronauts on several occasions to study various physiologic aspects of human spaceflight. On five separate occasions hurricanes caused major damage to the habitat, requiring significant structural repairs. In 2009 Aquarius was the scene of the third and final aquanaut death. This was caused by a malfunctioning oxygen sensor that had been affected by vibrations from a high frequency air powered drilling tool. Sadly, Aquarius closed in September 2012, bringing to an end a fifty year era of manned seafloor exploration and research. The 1960 had seen the dawn of a period of great excitement and expectation. Men would soon be expected to live and work in sophisticated and advanced seabed dwellings for extended periods. Endless military, commercial, industrial, and scientific opportunities appeared ready for the taking. For many different reasons this promise did not materialize but the practice of saturation diving lives on in several vital support settings. Other Uses of Saturation Diving Besides the above noted employment, saturation diving techniques have been used in three other unique and distinct settings. The U.S. Navy, having pioneered the science and practice of saturation diving technology, used this process in several secret missions during the Cold War. A nuclear submarine was SBT

19 adapted to incorporate a saturation living complex and an associated diver exit from saturation and the submarine capability. This was successfully used to intercept Soviet Union undersea communications cables that were transmitting data related to ballistic missile testing. The U.S. Navy has maintained saturation diving capability similar to that used in the oilfield (living in saturation on the deck of a support vessel and transferring to the work site in a diving bell). But, they rarely use it operationally. When various underwater search and recovery needs arise, the navy commonly sub contracts to civilian diving companies. In the late 1970 s, physicians at Duke University Medical Center, in North Carolina, U.S., used saturation diving techniques to treat complex and poorly responding cases of recreational SCUBA diving decompression sickness. This practice did not demonstrate superiority over more conventional methods and had a high degree of complexity and cost associated with it. Accordingly, it was discontinued in the 1980 s. The civil engineering aspect of saturation diving continues to remain viable today. Tunnel boring machines require manned support from time to time. If the tunnel is under significant pressure and/or the work requirement is long enough, saturation technology has proven to be a viable option to conventional surface orientated compression decompression procedures. SBT

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WEEK 11 CME323 NUMERIC ANALYSIS Lect. Yasin ORTAKCI yasinortakci@karabuk.edu.tr 2 INTERPOLATION Introduction A census of the population of the United States is taken every 10 years. The following table

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Lesson 23: How Ders 23: Nasıl Reading (Okuma) How are you? (Nasılsın?) How are your parents? (Ailen nasıl?) How was the interview? (Görüşme nasıldı?) How is your work? (İşin nasıl?) How do you go to school?

Going Home 02: At a Duty-free Shop Hi! How are you today? Today s lesson is about At a Duty-free Shop. Let s make learning English fun! Eve Dönüş 02: Duty-free Satış Mağazasında Exercise 1 Vocabulary and

Recap Çoğullar ler If the final vowel is a, ı, o or u, then use lar. limonlar, çocuklar If the final vowel is e, i, ö or ü, then use ler. zeytinler, ekmekler This, That, These and Those bu this bu limon

What Is Team Leadership? What Is Team Leadership? Team leadership is the management of a group of people brought together to work to achieve a common goal.in order to get everyone to work as one functioning

This empire began in 330 and lasted until 1453, for 1123 years. The Byzantine Empire began with the Emperor Constantine who reigned for thirteen years a total of 88 emperors were to reign during the course

The person called HAKAN and was kut (had the blood of god) had the political power in Turkish countries before Islam. Hakan was sharing the works of government with the assembly called kurultay.but the

Sokak Hayvanları yararına olan bu takvim, Ara Güler tarafından bağışlanan fotoğraflardan oluşmaktadır. Ara Güler All the photographs used in this calendar have been donated by Ara Güler for the benefit

a lot of lots of a great deal of plenty of çok, bir çok many much çok, bir çok a little little az, biraz a few few az, birkaç 1. A lot of; lots of; plenty of a lot of ( en yaygın olanıdır ), lots of, plenty

The Supporting People Logo Insanlari ve bagimsiz yasami destekleme The Supporting People Door in Watermark The Supporting People Introduction Helping you to live more independently Daha bagimsiz yasamak

Relative Clauses 1-3 a man who has powerful friends things I like the world which I created the kind of person we need a place that I know something you should know a place where life is simple somebody